Many operators are concerned about the amount of signalling coming from all smartphones and mobile users. When a user wants to send data, or is paged because of downlink data, he must go to ECM Connected (EPS Connection Management). This is done by sending a NAS Service request.
When the user is in ECM Connected, the users mobile/user equipment, UE, is known in eNodeB in Radio Access Network, RAN, after UE context setup. The eNodeB comprises an inactivity timer which times down until the UE is put into idle mode. In ECM Connected state, handovers are performed.
There could be high signalling load in Mobility Management Entity, MME, and Serving Gateway in Core Network, CN, when there are many UE context setup requests, pagings and S1 releases, when there are handovers. With a long inactivity timer there will be many handovers (and also battery drain) and with a fast release of the radio resources there will be many service requests, pagings and S1 releases.
In order to reduce the number of service requests, pagings and D1 releases, a longer timer could be used. A possible drawback is the drain of the battery capacity. It is possible to use DRX in ECM Connected mode in order to save battery. In order to handle UE's and use a shorter inactivity timer for those, it is possible to build a mobility history in the eNodeB of the visited cells since previous Service requests/Context setup.
However, a remaining drawback is that users that are moving will result in many handovers. So, for moving UE's a shorter time may be beneficial. Another drawback with the mobility handling in eNodeB is that the radio access information is lost at each S1-UE context release, where the subscriber goes to ECM idle mode.